How Will You Sleep Tonight? It's in Your Genes

Are you one of those people who rises before dawn and never needs an alarm clock? Or would you happily sleep until midmorning if you could? Do you feel like you are just hitting your stride by late afternoon, or do you get the day's main tasks accomplished by lunch?

Most of us have some degree of preference for late nights or early mornings. Where an individual falls on this spectrum largely determines his or her chronotype—an individual disposition toward the timing of daily periods of activity and rest. Some of us are clearly “larks”—early risers—while others are distinctly night owls. The rest of us fall somewhere between the two.

We’re now learning that these night owl and early riser tendencies are driven to some significant degree by biological and genetic forces. Different chronotypes are associated with genetic variations, as well as differences in lifestyle and mood disposition, cognitive function, and risks for health problems including sleep disorders and depression.

New research has found evidence of physical differences in the brains of different chronotypes. Scientists at Germany’s Aachen University conductedbrain scans of early risers, night owls, and “intermediate” chronotypes who fell in between the two ends of the spectrum—and discovered structural differences in the brains of people with different sleep-wake tendencies.

For the study, researchers observed 59 men and women—16 early risers; 20 intermediate sleepers; and 23 night owls. They found that, compared to early risers and intermediates, night owls showed reduced integrity of white matter—the fatty tissue that facilitates communication among nerve cells—in several areas of the brain. Diminished integrity of white matter in the brain has been linked to depression and disruptions of normal cognitive function.

Are Night Owls at Risk?

The cause of this difference in white-matter quality between night owls and other sleepers is not clear. Researchers speculate that the diminished integrity of white matter may be a result of the chronic “social jet lag” that characterizes the effects many night owls' sleep-wake routines—people who are disposed toward staying up late and sleeping late often find themselves at constant odds with work and school schedules that require early-morning starts. This can leave night owls chronically sleep deprived, experiencing many of the same symptoms of travel-induced jet lag, such as fatigue and daytime sleeplessness, difficulty focusing, and physical pain and discomfort.

Other research indicates that people who stay up late are at higher risk for depression, and are more prone to significant tobacco and alcohol use. They are also inclined to eat more, and to have less healthful diets than early risers or people with intermediate sleep patterns.

But it's not all bad news for night owls. Some studies have shown that people who stay up late are more productive than early risers, and have more stamina throughout the length of the day. Other research has shown that night owls display greater reasoning and analytical abilities than earlier-to-bed peers. And, on average, research shows, they achieve greater financial and professional success than those with earlier bedtimes and wake times.

Sleeping in Your Genes

This latest study is the first to offer physical evidence of neurological differences among people with different sleep tendencies. But other research has also shown that the inclinations toward staying up late or rising early are deeply rooted in biological and genetic differences:

Scientists have discovered an “alarm clock” gene that activates the body’s biological clock in the morning from its period of overnight rest. Identifying this gene and its function may tell us important new information about the influence of chronotype and circadian function on sleep and health.

Research has also revealed differences in brain metabolic function among night owls compared to early risers and middle-of-the-road sleepers. These were discovered in regions of the brain involved in mood, and may be one reason night owls are at higher risk for depression related to insomnia.

Scientists identified a gene variant that exerts a strong influence over the circadian clock, and the inclination to stay up late or rise early. This variation—which affects nearly the entire population—can shift the timing of an individual’s 24-hour sleep-wake cycle by as much as 60 minutes.

If our preferences for sleep and wake times are strongly influenced by genetics and biology, what are we to do when our inclinations don’t match up with the demands and responsibilities of our lives? Genetic forces appear to play an important role in our preferences, but we’re still working to understand just how, and how much. And we’re far from powerless: The choices we make about our sleep environments and sleep habits can make a significant difference. A recent study showed that limiting nighttime exposure to artificial light, and increasing exposure to daytime sunlight, can shift sleep-wake cycles earlier—even for night owls. Improved habits—being careful about alcohol consumption close to bedtime; sticking to regular sleep and wake times; making sure your bedroom is dark and free of electronic gadgets—can help reinforce your sleep schedule, even if it doesn’t align perfectly with your natural tendencies.

More broadly, I hope we’ll see society begin to recognize the power of these biological sleep patterns, and the need for flexibility to enable people to construct work and school schedules that align better with their dispositions toward sleep. This is a smart strategy that would be good for public health and productivity.

Bingo. I've always been a nightowl (couldn't ever get up for school as a kid) and have had depression come and go since I was about 10. The time where I was most mentally healthy was when I had more control over my schedule in college and could take late morning/afternoon classes. Every few months, there seems to be an article about how 'larks' are happier people. I'd be way happier and more balanced if the entire world was constructed around my schedule too!

I agree! This is one of quite a few ways I'm out of synch with the way the world seems to be scheduled. And yes, we would be a lot happier and less depressed if we could work around our natural sleep pattern. This is very similar to how the world is mainly constructed for extroverts. And yes, I am an introvert, and so this is yet another way I'm forced to go against my very nature. I wonder if night owls are mostly introverts and larks mainly extroverts?

Correlation is not causation. I wouldn't be surprised if the increased disruptions of normal cognitive function and reduced integrity of white matter had more to do with how I have spent my nights rather than when it is I actually fall asleep lol. The part about artificial light was cool though.

People also sleep around their day-to-day schedules. Many would prefer to go to bed earlier, but perhaps they have to work until late at night and other activities came up directly after. If they work until late, then they have to go to bed late. If their work starts early, they would most likely go to bed early. For those who schedule their morning classes at college, they will most likely go to bed earlier than those who schedule their classes later in the day. The hours you wake and the time you go to bed, is a personal choice. For many of us, our day-to-day schedule controls when we go to sleep, and I doubt very much it is all "genetic". Peers can be an influence too; we may try to correlate our sleeping patterns with those around us because it is more in the "norm" to go to bed at a certain time. I do believe that how ever we choose to live, the time we go to sleep will affect our brain structures and our brains will eventually adapt to the pattern we set for it.

I agree with limiting artificial light before bed time too - we can stay up for hours with the TV, phone, or lights on before we remember how tired we felt a few hours ago.

Our sleep schedule can be a flexible one, and in its entirety, genetics are not the main reason. Another example may be both the parents may go to bed earlier than their children, and their children see their examples of encouragement, but they choose not to follow. I've seen this happen many times. Like I said before, though, peers can have a great influence on how we live our lives on how and when we go to sleep.

I have always had trouble sleeping. When I was young I wondered if it was because I was born around 10am. Lol I have fought with depression my entire life, (chemical imbalance)which I was told was genetic. I clearly saw the genetic ties to the depression, but am having problems seeing the tie between sleep times and genetics. Both sides of my family were farmers, and for generations were forced to get up early. My father worked different shifts over his lifetime, but was almost always up before 6am. Just wondering. Really enjoyed the article though.

Perhaps more useful, and meaningful, results could be found by examining night owls who are able to follow their natural inclinations for sleep/wake cycles. I can't help wondering how much of the depression & other supposed effects of being a night owl are due to forcing your body into an unnatural pattern. Or perhaps depression leads to being a night owl. Or even some combination of these factors.

Another form of "control" & "society dictates" etc. Scientific? 23 people? What utter nonsense! I have been a Nightowl all my life! I don't drink, smoke, over eat, don't suffer from depression, sleep like a baby & relish the late hours when others are "sleeping"! Pure Bliss! Chose to work nights at times for the sheer pleasure of a near empty office to enjoy - so cosy! Also, would rather drive to my destination at night! Not be herded early morning like cattle onto packed trains or motorways & back again at night until you drop dead - therein lies the madness! Just prefer life to be simple - not the mad rat race which is the real culprit for the "bad habits" you list! How rude and judgemental! Not so long ago, folk had two chunks of sleep each night & got up to do all sorts in the middle of the night before the second sleep! Man, to his detriment, invented "the clock" as we know it, circa The Industrial Revolution to get more work out of the common people. And then, God forbid, the "9-5" routine. Even now, no-one has the brains to instigate "real flexible work-time" to reduce the traffic jams! The clue is in "Rush Hour"? DUH? We don't need nonsense "scientific" articles - just more common sense!

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I totally agree with Suzie. I'm a lifetime night owl, and until I retired I had to run the rat race. I was miserable, and by fridays I was so tired I would sleep all weekend to "catch up." Now that my time is my own, I am on a pretty predictable 6am-2pm sleep schedule. I'm always rested (unless I have to do other life things and wake up during that time). Bliss is a good word. When the sun goes down and it starts getting quiet, my body relaxes. I would also like to see a study of the "white matter" of night owls that are able to follow their natural sleep rhythm. I wish I could share this article with all the people in my life that called me lazy - especially my family when I was a child. They were wrong. Such a shame.

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I am a night owl trying to convert to an early riser. I am trying since almost two years. And I am able to fell asleep early, no problem. But when I wake up I have no energy... I still try, because I have to (my little daughter started school) but its hard. When I wake up early I never accomplish anything even if I have loads of time in the morning. Whether at night time I have energy to do anything. After reading this article I feel that I waste my time my trying..
But one thing is interesting, that if I wake up very early and get out of the house quickly to walk the dog, I get very energetic and can do leads after the walk. But I cant go out when my daughter is sleeping and only occasionally I could do that. She very often wakes early with me but there is no way she would go for a walk so early :)

You guys are sleepers. You go late, meaning you really think about what you do before bed, but then you go to bed early, like a little boy should. Then you wake early, possibly thinking about your day ahead. Regardless, you get up early. Also, it's creepy that we have to tell you the routine you just told us. What.

Just a thought, always struggled with depression and anxiety, but had periods of happiness. As a child I remember the first time I had to get up for school, it was shocking to me, I mean I felt so ill, like I was going to die. My mother would dress me while I was asleep. Then all these years I have forced myself into the world schedule. In the last few years I have had to get up increasingly early first at 6:30 am then at 5:45 and now at 5 Am and I have never been so physically ill and had some many emotional ups and downs. To be honest I am now curious if this schedule is making me ill????!!!! I should say I always aim for 8 hours sleep as that is what I need when not working.